Don't Blow Your Top (cooler, gallery plugs or oil filter)!! Many of you have "blown" apart your oil filter, cooler or even the oil passage plugs. What a mess! This is always costly, frustrating and time consuming especially when it seems to always blow the plug behind the flywheel. Why does this happen?
There could be a number of reasons. First, you need to understand how the oil system works. The stock oil pump must produce much more pressure than the engine requires to overcome restrictions and losses through the engine oil passages. It must also be capable of making up for wear as the engine gets old. This excess capability in a new engine is approximately 70 to 80% over the needs of a new or like new engine and is regulated by the oil pressure relief valve. VW has used two types of case designs to do specific jobs; the single and dual relief valve types. Actually both designs are excellent with the main difference being that the single type has both the directional (to the cooler or not to the cooler) and the regulating (excess spill off) valve as one unit. When the oil is cold this valve is pushed down past the 2nd bypass hole.
The top one is to allow oil to go to the engine without going through the cooler. The 2nd one (lower) actually passes the excess oil back to the sump near the cam gear area. The engine oil pressure is maintained by this "bypass" orifice. The factory was smart to design this bypass orifice to pass the specific volume of extra oil that the stock engine doesn't need to lube itself. Remember this point, as that's what this information is all about.
The dual oil pressure relief valve cases separate the two functions. The 1st valve (pulley end) still controls whether the oil goes to the cooler or not. The 2nd valve (flywheel end) regulates the oil pressure after it has gone past all of the rest of the engine's needs. This was necessary when they made the oil galleries larger in the block so the heads could receive a greater volume of oil to assist in cooling the smog controlled engines. This provides a higher constant pressure in the main oil gallery and follower area.
Again, the orifice is a specific size to allow the oil pressure to be maintained at a pressure that will protect the oil cooler, gallery plugs and full flow filter (if you have a filter that is an HP1 or equivalent). When you jack the oil pressure up with too large of an oil pump you override the capability of the bypass orifice.
If you put in stronger springs and/or different cup(s) combinations (which should never be done), you will restrict the orifice size or possibly close it off. Again, these are bandages on your elbow for a sore on your knee. If the engine is within factory tolerances, even the original factory smaller 21mm VW pump produces over 150 PSI (at the pump), which is more than adequate for any VW engine.
I've even seen some produce over 200 PSI and a 26mm make over 300 PSI when cold. Remember, if you are watching a pressure gauge in your car, it takes the reading after the relief valves and line loss restrictions and that's why you may only see 40 or 80 PSI on a gauge yet still have over 300 PSI at the pump, filter, etc. Those all come before the relief systems and that's where the majority of blow outs occur from the following areas:
1. When oil is too heavy for cold temperature.
2. When a super big pump is installed to make up for wear, running too hot or any other low oil pressure problem you have. When the oil is the coldest is when the possibility of a blow out is highest.
3. When using oversize oil pressure relief valve springs and/or cups.
Why not make the bypass orifice bigger? If enlarged to allow more passage of oil when cold, then there's too little pressure when the oil is warm. VW was extremely smart with this regulating system to control not only pressure, but directional control to bypass the cooler when cool, so do not mess with it unless you are a lot smarter than VW. That is the reason we designed the special Gene Berg relief cover.
The Gene Berg oil pressure relief valve pump cover handles all of these problems by going beyond the capability of the stock relief valve system. When the oil pressure reaches 125 PSI, it relieves directly back into the inlet side of the pump, maintaining 100 to 125 PSI (at the pump) even with cold oil and/or when bigger pumps such as our 30mm are used. This protects the filter, cooler, and galleries from surge blasts of over pressure when cold, yet maintains more than enough oil pressure when hot. Furthermore, it will not disrupt the redirection of the oil to the cooler (as all other fixes do) so the oil will properly warm up. The Gene Berg pressure relief valve oil pump cover can be used with full flow oil filters or installed for its safety relief valve feature alone.
Even better, it keeps the oil in the circuit so less oil is needed from the pickup tube. The oil is returned directly to the pump rather than being wasted off at the oil pressure relief hole location that is a long distance from the pickup tube. Originated and manufactured by Gene Berg from 1984. SW 2#